Multi-stage compressor airfoil aerodynamics. Part I - Airfoil potential flow analysis

Abstract

Potential-flow analysis of the airfoils in an axial flow compressor is an important element of the aerodynamic design. This type of analysis is used both as a tool in the optimization of new airfoil contours and also to predict the design and off-design performance of existing airfoil contours. The analysis is virtually exact in steady, twodimensional applications. The present paper assesses the ability of potential flow theory to predict the pressure distributions on rotor and stator airfoils in the unsteady, three-dimensional environment of a two-stage axial compressor. The paper demonstrates that while excellent agreement between the measured and computed results could be obtained in the core flow region, the unsteadiness and three-dimensionality produced by corner stall and rotor tip leakage can cause significant differences to occur. Nomenclature B = airfoil true chord Bx = airfoil axial chord CP = pressure coefficient (P-PToA) /Qum Cx = axial component of velocity cl = rotor tip clearance N = rotational speed P = pressure Q = incident dynamic pressure Qum = dynamic pressure based on midspan wheel speed: 1/2 pUlm r = radial distance Um = wheel speed at midspan x = axial distance a. = absolute yaw angle from axial (3 = relative yaw angle, from axial 6 circumferential coordiante 9 = flow yaw angle, from axial = flow pitch angle, from axial $ = flow coefficient, Cx/Um p = fluid density T = cascade pitch